Orthopedic intramedullary fixation system

ABSTRACT

A system and method for repairing fractured long bones. A guide wire is inserted through an opening drilled in a proximal bone segment and pushed through the intramedullary cavity of the proximal bone segment, across the fracture site and into the intramedullary cavity of a distal bone segment. A dilator is inserted over the guide wire and pushed through the intramedullary cavity into the distal bone segment to a stop at the distal end of the guide wire. A flexible tube having a radially expandable distal portion is then pushed over the guide wire into the distal bone segment and against the dilator. A compression nut is threaded over the proximal end of the guide wire to engage the proximal bone segment and compress the flexible tube. Compression of the flexible tube deploys the radially expandable distal portion to anchor the device in the distal bone segment.

FIELD OF THE INVENTION

This invention relates generally to an orthopedic support system andapparatus and more particularly to an intramedullary (IM) supportapparatus and method of use thereof for supporting fractured long bones.The IM support apparatus according to the present invention is minimallyinvasive and provides improved alignment of bone segments.

BACKGROUND OF THE INVENTION

Various methods and apparatus have long been used for positioning,stabilizing and supporting bone segments to repair bone fractures inhumans and animals. Simple external apparatus such as slings and splintsare well known and are still used alone or in combination with invasiveapparatus to repair broken bones. Slings are used alone in certaincircumstances where use of invasive apparatus or implants presents anunacceptable risk of injury to a patient. For example, slings are oftenused without any invasive apparatus to repair a fractured claviclebecause implantation of known invasive bone repair apparatus to repair afractured clavicle can risk life threatening damage to the patient'ssubclavian artery or damage to other vessels, nerves, nerve bundles,vital organs or surrounding tissues.

Since invasive repair of a fractured clavicle presents medical risk,patients having a fractured clavicle often forgo the benefits offered byvarious invasive apparatus and implants. Such benefits which includeimproved bone segment positioning, stabilizing and support promote morerapid recovery and reduce patient discomfort. Further, use of slingsalone often allows misaligned bone segments to heal such that a visiblyconspicuous deformation or a weak area remains which is susceptible tore-injury. Accordingly, it would be advantageous to provide a claviclerepair apparatus with reduced risk of injury to the patient.

Known invasive apparatus for bone segment repair include variousconfigurations of bone fracture reduction rods, orthopedic screws,intramedullary nails, intramedullary screws and the like. For example,U.S. Pat. No. 6,338,732 to Yang discloses an in-marrow nail structurehaving two threaded ends for drilling and engaging fractured bonesegments. A nut is screwed over a threaded proximal portion of thestructure to apply compressive force to the bone segments. The apparatusdisclosed in Yang and similar devices involve installing a drilling tipwithin the intramedullary cavity. These devices typically incorporatethreads having a cutting edge in at least a distal portion wherebydrilling is performed by rotating the devices around their longitudinalaxis. Accordingly, such devices are typically unsuitable forimplantation in curved bone segments. Such devices also present a highrisk of drilling through a bone segment into surrounding tissue, and aretherefore not well suited for use in repairing a fractured clavicle. Itwould be desirable to provide an intramedullary apparatus that issuitable for use in curved bone segments without presenting a high riskof damaging surrounding tissue.

In addition to providing a drilling capability for implanting anintramedullary device, the threaded distal portion of some known devicesserves as an anchor which secures the distal portion of the device to adistal bone segment. Bone segments are held together by also providing acompressing portion which engages the proximal bone segment and travelstoward the anchored distal portion.

In another type of known intramedullary support apparatus, an expandableanchor portion is provided for engaging the distal bone segment. Forexample, U.S. Pat. Nos. 3,779,239; 3,760,802 and 4,227,518 discloseparticular intramedullary retraction nails that include an expansionelement in their distal portion. The expansion elements serves as ananchor in a distal bone segment. The aforementioned devices aregenerally directed toward a rod disposed with a tubular portion.Relative linear motion between the rod and the tubular portion, such asby threading the rod to the tubular portion, causes actuation of theexpansion element to engage the bone lining in the distal portion. Abolt head and or nut and washer are installed over or incorporated withthe proximal portion of the rod which protrudes from a hole drilled inthe proximal bone segment. In the apparatus disclosed in U.S. Pat. Nos.3,779,239 and 3,760,802 the central rod is curved to correspond with thecurvature of the bone under repair.

Installation of a rod within the intramedullary cavity can increase therisk of damage to the bone lining, and can be difficult to perform oncurved bones such as the clavicle. Furthermore, apparatus heretoforeknown that are adapted for providing a distal anchor portion are notadapted for aligning a displaced fracture. Insertion of such devices toa misaligned fracture can cause increased separation of bone segmentsand possibly damage surrounding tissue. The rod's rigidity can alsoprevent it from centering radially when the expandable anchor portion isdeployed. Such devices can therefore allow a bone to heal in amisaligned or overlapped state which can be weak or appear deformed. Itwould therefore be desirable to provide a intramedullary support devicefor use on curved bone segments that does not include a rigid internalrod portion, and which is self centering and adapted to align bonesegments at a displaced fracture site.

Known IM fixation devices having an expandable anchor portion aretypically constructed with a number of separate moving components. Thenumber of moving components can make such devices expensive andsusceptible to malfunction. It would be desirable to provide an IMfixation device having an expandable anchor portion which does notrequire a large number of separate components.

The proximal portion of known IM fixation devices is often movablydisposed within the IM region of the proximal portion of a fracturedclavicle bone. Such proximal portions of the device protrude from theposterior lateral end of the clavicle bone. A stabilizing nut istypically rotated to engage the threaded portion of the IM fixationdevice, thus causing the stabilizing nut to partially traverse thethreaded portion of the IM fixation device. As the stabilizing nuttraverses the threaded portion, the stabilizing nut pushes the proximalportion of the fractured clavicle bone toward the distal portion of thefractured clavicle bone. The stabilizing nut is rotated until the distaland proximal portions of the fractured clavicle bone contact each other,such that the fractured ends of the clavicle bone remain in contact witheach other to allow for the accelerated healing of the claviclefracture.

Several heretofore known IM fixation devices include portions thatprominently protrude from the proximal lateral end of the clavicle bone.Even small movement of such devices can causes extreme pain to apatient. It would therefore be desirable to provide an intramedullaryfixation device that does not prominently protrude externally from thebone.

Installation of some known intramedullary support devices involvesinvasive surgery wherein a cut-down must be performed at the fracturesite. Such surgical installations increase the risk of infection,lengthen the recovery period, and often leave large unsightly scars. Itwould therefore be desirable to provide a method and apparatus forrepairing fractured bones which is minimally invasive and which does notrequire a surgical cut-down at the fracture site.

Many known intramedullary support devices are not fixed within theintramedullary space and can therefore suffer from migration within theintramedullary space. It has been known for intramedullary devices orcomponents thereof to migrate such that they pierce a patient'ssurrounding tissue, skin, or vital organs. It would therefore bedesirable to provide an intramedullary support device that does notsuffer from migration.

Many heretofore known intramedullary fixation devices are difficult toremove after a patient's fractured bone has healed. It would thereforebe desirable to provide an intramedullary support device that is moreeasily removed from the bone after a fracture has healed.

SUMMARY OF THE INVENTION

The present invention provides a method and apparatus for minimallyinvasive fixation and repair of fractured long bones. The term “longbone” is used generally throughout the present specification and ismeant to include any human or animal bone having sufficientintramedullary space for installation of the various embodiments of theinvention described below. For example, various embodiments of theinvention are described with respect to repair of a fractured collarbone in humans. It should be understood that the invention also includesa method and apparatus for repairing various other bones in humans inanimals such as bones in the upper and lower extremities as well assmaller bones, including bones in human hands and fingers.

According to an illustrative embodiment of the present invention, anopening is made into the intramedullary cavity toward a proximal end ofa proximal bone segment. A guide wire is inserted through the openingand pushed through the intramedullary cavity of a proximal bone segment,across the fracture site and into the intramedullary cavity of a distalbone segment. A dilator having longitudinal through-hole and a taperedleading surface is inserted over the guide wire and pushed through theintramedullary cavity into the distal bone segment to a stop at thedistal end of the guide wire. The tapered leading surface of the dilatoris adapted to aid in the alignment of bone segments as it is pushedacross the fracture site.

A flexible tube having a radially expandable distal portion is thenpushed over the guide wire into the distal bone segment and against thedilator. The expandable distal portion of the tube is deployed bycompressing the flexible tube between its proximal end and the dilator.Compression of the flexible tube can be performed by threading acompression nut onto the proximal end of the guide wire. The distal stopon the guide wire prevents the dilator and flexible tube from movingfurther distally so that compression is applied to the flexible tubebetween the dilator and the compression nut. The compression nut and/ora washer disposed with the compression nut are adapted to engage theproximal bone segment so that the proximal and distal bone segments arepulled together.

One embodiment of the present invention provides a bone segmentpositioning apparatus including a guide wire having a proximal end and adistal end. A distal stop is disposed on the guide wire about adjacentto the guide wire distal end. A proximal stop disposed on the guide wireabout adjacent to the guide wire proximal end. A tube is disposed overthe guide wire. The tube has a sidewall including a radially expandableanchor portion adapted for radial expansion upon compression of the tubebetween the distal stop and the proximal stop.

At least one embodiment also includes a dilator having a tapered distalsurface, an at least partially transverse proximal surface and a tubularinner surface defining a longitudinal through hole. The dilator isdisposable on the guide wire wherein the guide wire extends through thethrough hole. The at least partially transverse proximal surface servesas the distal stop. In a particular embodiment, the at least partiallytransverse proximal surface can also be countersunk to accept the tube.

The tapered distal surface can include means to prevent rotation of thedilator relative to the guide wire. Such means can be manifest, forexample in a hexagonal depression in the tapered surface that mates witha hexagonal anti-rotation feature fixed to the guide wire. For examplein one embodiment, the guide wire includes a spherical distal tip havinga diameter greater than the diameter of the longitudinal through hole.The means to prevent rotation in this embodiment include a polygonalmating surface of the tapered surface adapted to fit an oppositegendered polygonal mating surface of the spherical distal tip. Personshaving ordinary skill in the art should appreciate that a large numberof anti-rotation features such as key/slot features, interference fits,wedges and the like could be substituted as anti-rotation means withinthe scope of the present invention.

In one embodiment, the tube and guide wire are flexible. The proximalstop is formed as a distal surface of a compression fastener over theproximal end of the guide wire. The compression fastener comprises atleast one nut threaded onto the proximal end of the guide wire. Theradially expandable anchor portion includes a plurality of rib portionsformed between a plurality of longitudinal slots disposed through thesidewall. The radially expandable anchor portion is disposed toward thedistal end for engagement with a distal bone segment.

In an illustrative embodiment, the rib portions include at least onereduced section formed in a central portion of each rib segment. The atleast one reduced section can include a crease formed transverselyacross the central portion of each rib segment. Alternatively the atleast one reduced section comprises a narrowed section of each ribsegment. The at least one reduced section could also be creased andnarrowed, for example.

In a particular embodiment, the plurality of rib portions comprise atleast two evenly spaced rib portions. The radially expandable anchorportion is also adapted to collapse upon relaxation of compressionforces between distal and proximal segments of the tube. In anotherembodiment, the radially expandable anchor portion is adapted tocollapse upon application of tension between distal and proximalsegments of the tube.

In another embodiment, the invention provides a method for aligningfractured bone segments. The method includes installing a tube in anintramedullary space spanning a fracture, anchoring a portion of thetube to a first side of the fracture, and compressing the tube toradially expand an expandable anchor portion of the tube on a secondside of the fracture.

In one embodiment, the method also includes installing a guide wire inthe intramedullary space spanning the fracture. The tube is installedover the guide wire and compressed between stops on the guide wire.Anchoring a portion of the tube to a first side of the fracture can beperformed, for example, by installing an anchor nut which engages thebone segment over a proximal end of the guide wire. The method can alsoinclude installing a tapered dilator over the guide wire prior toinstalling the tube over the guide wire. The dilator includes atransverse portion which serves as one of the stops.

In the illustrative embodiment of the invention, the method alsoincludes drilling into the intramedullary space in a proximal bonesegment; and reaming the intramedullary space. The method can alsoinclude releasing compression on the flexible tube to allow theexpandable anchor portion to retract for removal of the tube and guidewire upon healing of the bone segments.

Advantages of the invention include provision of a bone segmentpositioning device and methodology that involves a safer, minimallyinvasive surgical procedure which allows for substantially less pain anddiscomfort for a patient. Further advantages of the invention includethe ability to repair fractured bones without the need for “cut-down” atthe fracture site, thus greatly reducing or eliminating any nerve andblood vessel disturbance and risk of infection. An additional advantageof the invention is that the bone segment positioning device is easilyremovable and malleable. The malleability of the device adds an extradegree of safety because the device will bend rather than applyingpotentially damaging lateral pressures in the IM cavity.

The present invention overcomes the deficiencies of the prior art byproviding a clavicle repair apparatus with reduced risk of injury to thesubclavian artery. An intramedullary apparatus is provided that issuitable for use in curved bone segments without presenting a high riskof damaging surrounding tissue. The various embodiments of the presentinvention also provide an intramedullary support device for use oncurved bone segments that does not include a rigid internal rod portion,and which is self centering and adapted to align bone segments at adisplaced fracture site.

Further, the present invention provides an IM fixation device having anexpandable anchor portion which does not require a large number ofseparate components and does not prominently protrude externally fromthe bone. The various embodiments of the present invention also providea method and apparatus for repairing fractured bones which is minimallyinvasive and which does not require a surgical cut-down at the fracturesite

BRIEF DESCRIPTION OF DRAWINGS

The foregoing and other features and advantages of the present inventionwill be better understood from the following detailed description ofillustrative embodiments, taken in conjunction with the accompanyingdrawings in which:

FIG. 1 is a side cross sectional view of a long bone compressionapparatus according to an illustrative embodiment of the presentinvention;

FIG. 2 is a plan view of a guide wire according to an illustrativeembodiment of the present invention;

FIG. 3 is a cross sectional view of a dilator according to anillustrative embodiment of the present invention;

FIG. 4 is a cross sectional view of an inner tube according to anillustrative embodiment of the present invention;

FIG. 5 is a cross sectional view of an outer tube according to anillustrative embodiment of the present invention;

FIG. 6 is a cross sectional view of an interface washer according to anillustrative embodiment of the present invention;

FIG. 7 is a cross sectional view of a compression nut according to anillustrative embodiment of the present invention;

FIG. 8 is a cross sectional view of a fractured long bone illustratingthe method of inserting a guide wire according to an illustrativeembodiment of the present invention;

FIG. 9 is a cross sectional view of a fractured long bone illustrating amethod of installing a dilator according to an illustrative embodimentof the present invention;

FIG. 10 is a cross sectional view of a fractured bone segment having aguide wire and a dilator installed according to an illustrativeembodiment of the present invention;

FIG. 11 is a cross sectional view of a fractured bone segment having aguide wire, dilator and outer tube installed in the intramedullarycavity according to an illustrative embodiment of the present invention;

FIG. 12 is a cross sectional view of a fractured long bone having anintramedullary fixation apparatus according to an illustrativeembodiment of the present invention installed therein with an expandedanchor portion;

FIG. 13 is a cross sectional view of a drill guide suitable for use inmethods of installing the intramedullary device according to the presentinvention;

FIG. 14 is a cross sectional view of a fractured long bone having anintramedullary fixation apparatus installed therein and illustrating theuse of an external fixation device in conjunction with theintramedullary fixation apparatus according to an illustrativeembodiment of the present invention; and

FIG. 15 is a pictorial view of a partially assembled intramedullaryfixation apparatus according to an alternative embodiment of theinvention including an outer tube having a plurality of semi-annularcuts.

DETAILED DESCRIPTION OF THE INVENTION

In FIG. 1, the components of a long bone compression apparatus 10 havinga proximal end 12 and a distal end 14 according to the an illustrativeembodiment of the invention are shown assembled together in a crosssectional view. A guide wire 16 extends from the distal end 14 to theproximal end 12 of the compression apparatus and includes a threadedportion 17 on the proximal end of the guide wire 16 and a distal endstop 18 disposed on the distal end of the guide wire 16. A dilator 20 isdisposed over the guide wire 16 adjacent to the distal end stop 18. Asdisclosed herein, the term ‘distal’ refers to the element or portionfurthest from the threaded portion 17 of the guide wire 16 and the term‘proximal’ refers to the element or portion closest to the threadedportion 17 of the guide wire 16.

In the embodiment shown in FIG. 1, an inner tube 21 is disposed over theguide wire 16 and an outer tube 22 is disposed over the inner tube 21.Both the inner tube 21 and outer tube 22 abut the dilator 20. Aninterface washer 24 is disposed over the threaded portion of the guidewire and abuts the proximal end of the outer tube 22. A nut 26 isthreaded onto the threaded portion 17 of the guide wire 17 and abuts theinterface washer 24. At least one slot 28 extends through the outer tube22.

In FIG. 2, an illustrative embodiment of a guide wire 16 according tothe present invention is shown. The guide wire 16 includes a distal endstop 18. The end stop 18 can be formed integrally with the guide wire 16or can be a separate component assembled securely thereto. In theembodiment of FIG. 2, the end stop has a spherical shape. Personsskilled in the art should appreciate that the end stop could be made invirtually any shaped radial protrusion of sufficient length formed withor fixed to the distal end of the guide wire. The end stop 18 mustextend radially beyond the outside surface of the guide wire by adistance greater than the diameter of a through hole in the dilator 20through which the guide wire passes.

In at least one embodiment of the invention, the end stop 18 includesanti-rotation surfaces such as a hexagonal outside surface for matingwith a hexagonal cavity in the dilator. In another embodiment, the endstop 18 can be formed as a T shape at the distal end of the guide wire.The T shaped end stop can prevent rotation of the dilator 20 relative tothe guide wire 16 if a dilator 20 having a mating slot in its distalportion which accepts the T shaped end stop.

The proximal end of the guide wire has a threaded exterior surface forengagement with a compression nut. In the illustrative embodiment thethreads are a 0-80 UNF thread extending 0.620 inches from the proximalend of the guide wire. Persons skilled in the art should appreciate thata number of different thread sizes could be substituted for engagementwith a compression nut according to the present invention and that thethreads can extend along a length shorter or longer than the lengthshown in FIG. 2. It is envisioned, for example, that an alternativeembodiment of the invention could be constructed using a guide wirehaving a threaded surface along its entire length.

In the illustrative embodiment, the guide wire has a circular crosssection and is made from TI6AL-4AV ELI Alloy per ASTM F160. Personsskilled in the art should appreciate that the guide wire couldalternatively be made from a number of clinically suitable materialssuch as stainless steel, molded or extruded polymers and the like. It isenvisioned that a guide wires having a different cross sectionalgeometry can also be used in alternative embodiments of the invention.For example, it is envisioned that a flat steel band could besubstituted for a circular cross sectional guide wire in alternativeembodiments of the invention. Although the guide wire is describedherein generally in terms of a flexible wire, persons skilled in the artshould appreciate that the guide wire can be made from a flexible rod orelongated flexible structure.

In FIG. 3, an illustrative embodiment of a dilator 20 according to thepresent invention is shown. In the illustrative embodiment, the dilator20 has a circular cylindrical body portion 22 and a tapered distalportion 24. A cylindrical through hole 26 extends through the center ofthe dilator along its longitudinal axis. The through hole diameter isgreater than the diameter of the guide wire to facilitate travel of thedilator along the guide wire up to the distal end stop of the guidewire.

The dilator 20 can also include one or more counter bores in itsproximal end to accept one or more tubes disposed over the guide wire.In the embodiment shown in FIG. 3, the dilator 20 includes an innercounter bore 28 for accepting an inner tube disposed over the guide wire16 and an outer counter bore 30 for accepting an outer tube disposedover the guide wire 16. In the illustrative embodiment, the counterbores include tapered portions adapted for mating with tapered distalends of a respective tube.

In the embodiment shown in FIG. 3, the dilator 20 includes a transverseslot 32 extending across its tapered distal portion 24. The slot 32 isadapted to accept an anti-rotation surface of the guide wire end stop18. In the illustrative embodiment, the dilator 20 is made from TI6AL-4VELI Alloy per ASTM F133. Persons skilled in the art should appreciatethat a number of alternative materials could alternatively be used tofabricate a dilator 20 according to the present invention. For example,stainless steel or medically suitable polymers and the like can be usedto fabricate a dilator 20 within the scope of the present invention

In FIG. 4, an inner tube 21 as used in a particular embodiment of thepresent invention is shown. The inner tube 21 has a tapered distal end34 for engagement with the inner counter bore 28 (FIG. 3) in the dilator20. An internal cavity 36 adapted for sliding over the guide wire 16extends along the full length of the inner tube 21 along itslongitudinal axis. Alternatively, it is envisioned that the inventioncould also be practiced using a guide wire and inner tube that areengaged by threading one with the other. In such an embodiment athreaded internal cavity is adapted for threading onto a threaded guidewire.

In the illustrative embodiment shown in FIG. 4, the inner tube 21 ismade from nitinol tubing having a 0.090″ outside diameter and a 0.062″inside diameter. Nitinol is a particularly suitable material for use incomponents of an IM fixation device because it has stress/straincharacteristics that approximate the stress/strain characteristic ofhuman and animal bones. Persons skilled in the art should appreciatethat a number of different materials could be used having a number ofdifferent inside and outside diameters to substitute for theillustrative inner tube 21 within the scope of the present invention.

Since a function of the inner tube 21 in an illustrative embodiment isto push the dilator 20 along the guide wire 16 to the distal stop 18,inner tube material and inner tube dimensions of such embodiments shouldhave sufficient rigidity to force the dilator 20 along the guide wire 16even when resistance is presented by friction in the IM cavity, forexample when the dilator traverses a misaligned fracture site. Inembodiments of the invention intended for use in curved long bones, theinner tube 21 should be sufficiently flexible to travel around curves inthe IM cavity of the curved bone. Although the various embodiments ofthe invention are described herein as having an inner tube 21 with agenerally circular cross-section, persons skilled in the art shouldappreciate that an inner tube having a different cross-sectional shape,such as for example, an oval or polygon could be substituted thereforewithout departing from the spirit and scope of the invention.

In FIG. 5, an illustrative embodiment of an outer tube according to thepresent invention is shown. The outer tube 22 has a tapered distal end38 for engagement with the outer counter bore of the dilator 20.Alternative embodiments of the invention can be practiced using an outertube 22 without a tapered distal end. For example, persons skilled inthe art should appreciate that certain embodiments of the presentinvention can be practiced without any counter bore in the dilator 20.In these and other alternative embodiments, an outer tube 22 having anon-tapered distal end can be used.

An internal cavity 40 adapted for sliding over the inner tube 21 extendsalong the full length of the outer tube 22 along its longitudinal axis.Persons skilled in the art should appreciate that the internal cavity 40could alternatively be threaded for engagement with an inner tube 21having a threaded outer surface. In other alternative embodiments of thepresent invention no inner tube 21 is used. In such embodiments, theinternal cavity 40 of the outer tube 22 is adapted for sliding over orthreading over the guide wire.

In the embodiment shown in FIG. 5, the outer tube 22 is made fromnitinol tubing having a 0.140″ outside diameter and a 0.105″ insidediameter. Persons skilled in the art should appreciate that a number ofdifferent materials could be used having a number of different insideand outside diameters to substitute for the illustrative inner tube 21within the scope of the present invention. In embodiments of theinvention intended for use in curved long bones, the outer tube 22should be sufficiently flexible to travel around curves in the IM cavityof the curved bone. Although the various embodiments of the inventionare described herein as having an outer tube 22 with a generallycircular cross-section, persons skilled in the art should appreciatethat an inner tube having a different cross-sectional shape, such as forexample, an oval or polygon could be substituted therefore withoutdeparting from the spirit and scope of the invention.

At least one slot 42 defines an anchor portion of the outer tube. In theillustrative embodiment, four slots having uniform annular spacingextend through the outer tube toward the proximal end of the tubing todefine the anchor portion 44. The four slots 42 define four ribs 46therebetween which are designed to collapse radially outward uponcompression of the outer tube between its ends. In an illustrativeembodiment of the invention, the four ribs are also designed to regaintheir approximate original shape upon relaxation of the compressiveforce.

In the illustrative embodiment shown in FIG. 5, the slots are 1″ longand 0.062″ wide having a full radius at either end. Persons skilled inthe art should appreciate that various rib dimensions by the variousslot dimensions and various numbers of ribs and slots can be used inalternative embodiments of the present invention. It should beunderstood that the rib 46 and slot 42 dimensions are critical to thefunctionality of the anchor portion 44 and will depend upon themechanical properties of the material used for fabricating the outertube and the thickness of the outer tube wall.

In other alternative embodiments of the present invention slots betweenthe ribs 46 of the anchor portion 44 are shaped to define a foldinglocation on the rib 46. For example the slots 42 can have a widersection at the midpoint of their length to create a narrower portion ofeach rib 46 formed between two such slots 42. The narrower portion ofsuch ribs 46 at the midpoint of their length can provide a foldinglocation on the rib 46. Other structures that could be used to create afolding location include an internal annular groove, an external annulargroove, a perforation, an embossment or the like. It is envisioned thatin still another embodiment of the present invention, a folding portioncan be formed by dividing ribs 46 at the folding location and installinga hinges between rib segments.

It is envisioned that alternative embodiments of the invention willinclude gripping portions (not shown) configured on one or more of theribs 46 to provide increased friction between the anchor portion 44 andthe intramedullary wall. For example, it is envisioned that alternativeembodiments of the invention will include textured rib portions,serrated rib portions and the like for improved engagement with theintramedullary wall when the anchor portion 44 is deployed.

Although the various embodiments of the invention are described hereinin terms of a single anchor portion 44, it is envisioned thatalternative embodiments of the invention will be practiced using morethan one anchor portion 44 disposed along the outer tube 22. Inalternative embodiments, it is envisioned that the additional anchorportions (not shown) can be configured with different dimensions tocause a specific sequence of engagement upon application of compressiveforces to the outer tube 22.

In FIG. 6, an interface washer 24 according to an illustrativeembodiment of the present invention is shown. The interface washerincludes a through hole 50 extending along its longitudinal axis. Thethrough hole 50 is adapted to fit over the guide wire 16. In analternative embodiment the through hole 50 of the interface washer 24can be threaded for threading engagement to a threaded portion of theguide wire 16. A concave proximal surface 52 is adapted for alignmentwith a convex distal surface 64 of a compression nut 26 (FIG. 7).

Persons skilled in the art should appreciate that alternativeembodiments of the present invention can be practiced by providing aconvex proximal surface on the interface washer 24 and a concave distalsurface on the compression nut 26 without including a concave or convexproximal surface in the interface washer 24 and/or compression nut 26.For example, it is envisioned that an interface washer having a flatproximal surface can be used with a flat compression nut withoutproviding any alignment between the compression nut and interfacewasher. Alternatively a number of different surface combinations can beused to provide alignment between the interface washer and thecompression nut while allowing relative rotation therebetween.

In the illustrative embodiment shown in FIGS. 1 and 6, a step 54 isformed between a first outside diameter 56 adapted for fitting to theinside diameter of the outer tube 22 and a bone interface surface 58.The step 54 defines a compression surface 60 which abuts the proximalend of the outer tube 22. In the illustrative embodiment, the boneinterface surface 58 is tapered outward in the proximal direction. Thebone interface surface 58 engages a proximal bone segment by beingpressed into a hole drilled in the proximal segment when a compressionnut 26 is threaded to the guide wire 16. The outward tapering of thebone interface surface 58 in the illustrative embodiment allows thewasher to be partially inserted into a drilled entry hole in a proximalbone segment to secure the proximal end of the apparatus 10 (FIG. 1) tothe proximal bone segment.

Persons skilled in the art should appreciate that the present inventioncan be practiced using a number of different types of bone interfacesurfaces. For example, it is envisioned that a stepped surface havingserrations could be used as a bone interface surface in an alternativeembodiment of an interface washer according to the present invention. Inthe alternative embodiment, the stepped surface would include a firstsurface fitting into the drilled entry hole and the step surface widerthan the drilled entry hole having serrations for engaging the outsideof the proximal bone.

Flat portions 62 are provided on the surface of the interface washer 24for engagement with an anti-rotation tool such as a wrench. In theillustrative embodiment shown in FIG. 6, a pair of parallel flatportions 62 are suitable for engagement with a wrench, pliers or otheranti-rotation tool. Persons skilled in the art should appreciate that anumber of different surface configurations can be provided on theinterface washer to prevent rotation of the washer while the compressionnut is installed. For example, the pair of flat portions 62 can bereplaced by a hexagonal or other polygonal surface adapted forengagement by a wrench or a knurled surface adapted for being gripped byhand. Alternatively, it is envisioned that one or more radial arms couldbe provide extending from the proximal portion of the interface washer24 for gripping to prevent rotation of the interface washer 24 when thecompression nut 26 is installed.

In the illustrative embodiment, the interface washer is made fromTI6AL-4V ELI ALLOY PER ASTM F136. Persons skilled in the art shouldappreciate that an interface washer 24 according to the invention couldalternatively be made from a number of different clinically suitablematerials such as stainless steel, thermoplastic or the like.

In FIG. 7, a compression nut 26 according to the present invention isshown. The compression nut 26 includes a convex distal surface 64adapted for alignment in the concave proximal surface 52 of theinterface washer 24. A threaded through hole 66 extends along thelongitudinal axis of the compression nut 26. The threaded through holeis adapted for threading onto the threaded portion of the guide wire.Flat surfaces are provided for engagement with a rotation tool such as awrench, nut driver, pliers or the like.

Persons skilled in the art should appreciate that a number of differentshaped tool engagement surfaces may be provided on the compression nut26 for engaging a tool adapted to the particular shape for threading thecompression nut 26 on the guide wire 16. It is also envisioned that theflat surfaces 68 can be replaced by a knurled surface adapted for beinggripped by hand. Alternatively, it is envisioned that one or more radialarms could be provide extending from the compression nut 26 to aid inmanual threading of the compression nut onto the guide wire 16.

In the illustrative embodiment shown in FIG. 7 the compression nut ismade from TI6AL-4V ELI ALLOY PER ASTM F136. Persons skilled in the artshould appreciate that a compression nut 26 according to the inventioncould alternatively be made from a number of different clinicallysuitable materials such as stainless steel, thermoplastic or the like.

A method of using the present invention will be described first withrespect to FIGS. 8-12. It should be understood by persons skilled in theart that the methods of installing the present invention can be bestperformed using imaging technology such as fluoroscopic imagingtechniques, ultrasonic imaging or the like to monitor positions of thevarious components of the apparatus during installation. As shown inFIG. 8, a hole 70 is drilled through the bone wall 71 into the IM cavity76 toward the proximal end of a proximal bone segment 72 of a fracturedbone. It should be understood the in the context of this disclosure theterms broken and fractured used in conjunction with a bone includes butis not limited to greenstick fractures, displace fractures, plasticdeformity, torus (buckle) fractures, growth plate fractures, closedfractures, open (compound) fractures, comminuted fractures, pathologicalfractures, stress fractures and the like.

The hole 70 must be wide enough to allow passage of the dilator 20,guide wire 16, outer tube 22 and (optionally) inner tube 21 but narrowenough to engage the bone interface washer 24 of the apparatus 10.

In at least one embodiment of the invention a drill guide is used toalign a drill bit at a constant orientation relative to the bone whiledrilling and to prevent the drill bit from drilling beyond the IMcavity. An exemplary drill guide 80 for use in the illustrative methodof installing intramedullary support apparatus 10 of the presentinvention is shown in FIG. 13. The drill guide includes a hollow shaft82 adapted for guiding a drill bit. The hollow shaft has a boneengagement surface 84 which can include features such as serrations toprevent slippage on the exterior surface of a bone. The hollow shaftalso has a drill stop surface 86 displaced from the bone engagementsurface 84 by a distance determined to allow a drill bit to enter the IMcavity but to prevent the drill bit from drilling beyond the IM cavity.A handle 88 extending from the shaft 82 allows the drill guide to besecurely held in place during a drilling procedure.

Once the hole is drilled, a guide wire 16 is inserted into the IM cavityand manually pushed across the fracture site 78 into the distal bonesegment 74. The proximal portion of the guide wire 16 remains extendingoutside of the drilled hole 70. A dilator 20 is installed over theproximal end of the guide wire 16 and pushed into the IM cavity 76,across the fracture site 78 and into the IM cavity 76 of the distal bonesegment 76.

In at least one embodiment of the invention, as shown in FIG. 9, aflexible tube is used to push a dilator along the guide wire. A handle92 can be used to allow better gripping leverage to manually push theflexible tube 90 from the proximal end. As the tapered distal portion ofthe dilator crosses a fracture site, the tapered surface engages thebone wall of the distal bone segment and tends to align the fracturedbone segments with each other. As shown in FIG. 10, the dilator ispushed to the end stop disposed on the distal end of the guide wire. Inthis illustrative embodiment the flexible tube is removed once thedilator reaches the end stop.

In an alternative embodiment, using an inner tube 21, the inner tube isused to push the dilator through the IM cavity. The inner tube 21 isthen left in place and becomes part of the bone fixation apparatus 10.

Next, as shown in FIG. 11, an outer tube 22 is installed by pushing theouter tube over the guide wire (and over the inner tube 21 if an innertube is installed). The outer tube is pushed as far as possible until itis stopped by the proximal surface of the dilator 20.

Once the outer tube 22 is fully installed, a bone interface washer isinstalled over the proximal end of the guide wire 16. A compression nutis then placed over the proximal end of the guide wire and threadedalong the threaded portion of the guide wire. In the illustrativeembodiment, the bone interface washer is wedged into the hole and heldfixed while the compression nut is turned. When the compression nutreaches is prevented from traveling distally by the compression nut,further threading of the nut causes the nut to pull the guide wire inthe proximal direction.

While the proximal end of the outer tube 22 is prevented from movingdistally by the bone interface washer 24, the distal end of the outertube is pulled distally by the guide wire 16 and dilator 20. The outertube 22 is thereby subject to a compressive force which causes theanchor portion 44 to deploy i.e. as the ribs 46 of the outer tube 22fold radially outward (FIG. 12). Once the anchor portion 44 deploys, itengages the inner surface of the bone (i.e. the outer wall of the IMcavity) in the distal bone segment. Further turning of the compressionnut 26 causes the engaged distal bone segment 74 to be pulled againstthe proximal bone segment 72 thereby securing the fracture site under acompressive force.

In the alternative embodiment of the invention having an inner tube 21(FIG. 4) disposed over the guide wire 16, the inner tube 21 can have alength relative to the length of the outer tube adapted so that theinner tube abuts the bone interface nut when an optimal anchordeployment condition is reached or to stop excessive advancement of thecompression nut 26. In another alternative embodiment, the threadedportion 17 of the guide wire 16 extends only long enough along the guidewire 16 to allow optimal advancement of the compression nut 26 andthereby cause optimal engagement of the anchor portion 44.

In an alternative method of installing the apparatus according to thepresent invention, an external reduction device is used to hold bonesegments in place while the IM device 10 is installed. As shown in FIG.14, the external fixation device includes a pair of telescoping tubes102, 104 and a pin 106, 108 extending from the end of each telescopingtube 102, 104 into a respective bone segment. The pins 106, 108 areinstalled in holes drilled in each bone segment using fluoroscopicimaging as known in the art. An adjustment nut 110 causes thetelescoping tubes 102, 104 to translate toward each other causing acompressive force between the bone segments. The external reductionapparatus 100 is left in place during installation of the IM bonefixation apparatus 10 of the invention and removed once the IM bonefixation apparatus 10 is in place.

In embodiments of the invention intended for use in to repair curvedbones, it should be understood by persons skilled in the art that theguide wire 16, inner tube 21, and outer tube 22 should have sufficientflexibility to allow each of these components to be installedsequentially in the IM space the curved bones. Once installed thecombined strength and rigidity of these components provide the structurenecessary for maintaining compression and providing strength to the boneunder repair.

In an alternative embodiment of the invention shown in FIG. 15, one ormore semi-annular 120 cuts are provided in the outer tube 22 to increaseflexibility for installation in the IM space curved bones. Suchsemi-annular cuts 120 increase flexibility in the outer tube 22 whilemaintaining strength in compression that is necessary to causedeployment of the anchor portion 44. Persons skilled in the art shouldappreciate that various similar structures can be substituted for thesemi-annular cuts 120 according to the alternative embodiment within thescope of the present invention.

It is completed in the practice of this invention that, in particularembodiments, the devices of this invention will be coated, in whole orin part, with bioactive material. As used herein bioactive materialshall be broadly construed to include, without limitation,immunomodulators such as a cyclosporine, anti infectives such asantiviral or antibiotic compounds, angiogenic or antiangiogeniccompounds, growth factors, antineoplastics compounds, compounds toencourage or prevent the adherence (or infiltration) of the device tothe surrounding tissue, and other therapeutic agents. Further includedare coatings to improve detection of the device such as radiopaquecoatings and contrast media. Further contemplated are biodegradablecoatings and coatings which may be impregnated with bioactive agents.

While the invention has been described with reference to an exemplaryembodiment, it should be understood by those skilled in the art thatvarious changes, omissions and/or additions may be made and equivalentsmay be substituted for elements thereof without departing from thespirit and scope of the invention. In addition, many modifications maybe made to adapt a particular situation or material to the teachings ofthe invention without departing from the scope thereof. Therefore, it isintended that the invention not be limited to the particular embodimentdisclosed for carrying out this invention, but that the invention willinclude all embodiments falling within the scope of the appended claims.The teaching of all references cited herein are incorporated herein byreference.

1.-23. (canceled)
 24. A method for aligning bone segments comprising:installing a tube in an intramedullary space spanning a fracture;anchoring a portion of said tube to a first side of said fracture;compressing said tube to radially expand an expandable anchor portion ofsaid tube on a second side of said fracture.
 25. The method according toclaim 24 further comprising: installing a guide wire in saidintramedullary space spanning said fracture; wherein said tube isinstalled over said guide wire; and wherein said tube is compressedbetween stops on said guide wire.
 26. The method according to claim 25further comprising installing a tapered dilator over said guide wireprior to installing said tube over said guide wire; wherein said dilatorincludes a transverse portion which serves as one of said stops.
 27. Themethod according to claim 25 wherein said step of anchoring a portion ofsaid tube to a first side of said fracture comprises installing ananchor nut over a proximal end of said guide wire.
 28. A method foraligning fractured bone segments comprising: installing a guide wire inan intramedullary space spanning said fracture; installing a flexibletube over said guide wire in said intramedullary space spanning afracture; anchoring a portion of said flexible tube to a first side ofsaid fracture; compressing said flexible tube to between stops on saidguide wire to radially expand an expandable anchor portion of saidflexible tube on a second side of said fracture.
 29. The methodaccording to claim 25 further comprising installing a tapered dilatorover said guide wire prior to installing said tube over said guide wire;wherein said dilator includes a transverse portion which serves as oneof said stops.
 30. The method according to claim 25 wherein said step ofanchoring a portion of said tube to a first side of said fracturecomprises installing an interface washer over a proximal end of saidguide wire.
 31. The method according to claim 25 further comprising:drilling into said intramedullary space in a proximal bone segment; andreaming said intramedullary space.
 32. The method according to claim 25further comprising: releasing compression on said flexible tube to allowsaid expandable anchor portion to retract for removal of said tube andguide wire upon healing of said bone segments.